A spark plug may be coupled to a cylinder of an internal combustion engine to ignite a compressed air and fuel charge within the cylinder. A spark plug may be considered fouled when an insulator nose at the firing tip of the spark plug is covered with a foreign substance such as fuel, oil, and/or carbon residue. A fouled spark plug may cause misfire, resulting in loss of power and increased vehicle emissions.
Other attempts to address spark plug fouling include controlling engine operation based on operation in a previous run period. One example approach is shown by Ma et al. in U.S. Pat. No. 8,150,604 B2. Therein, a spark fouling condition is determined based on fuel mass during the previous engine run period, between a start and stopping of the engine. In response to spark fouling condition, engine parameters such as air-fuel ratio and spark timing are adjusted while the engine is running.
However, the inventors herein have recognized potential issues with such method. As one example, the prior method may not be able to address spark plug fouling during the pre-delivery phase of a vehicle. Due to pre-delivery plant marshalling, the engine may be started multiple times without sufficient warming up. The excessive number of engine starts may contribute significant amounts of deposits to the spark plugs and yield fouled plugs. Spark plug fouling in the pre-delivery phase may end up with misfire and check engine lights displayed in new vehicles, which may lead to new vehicle owner dissatisfaction and increased warranty costs. Further, due to the limited engine run period in the pre-delivery phase, prior spark fouling mitigating methods may not be effective in fully cleaning up the spark plug fouled during the pre-delivery phase.
In one example, the issues described above may be addressed by a method comprising: during a pre-delivery phase of a vehicle, increasing a spark plug fouling index saved in a nonvolatile memory in response to an engine start; and operating the engine to clean the spark plug in response to the updated spark plug fouling index being higher than a threshold. In this way, spark plug fouling may be identified and the fouled plug may be cleaned before delivering the vehicle to the dealership before and/or in addition to post-delivery fouling cleaning operations.
As one example, a vehicle may be set, either manually or automatically, in a pre-delivery mode before being delivered to the dealership. While the vehicle is in the pre-delivery mode, in response to each engine start, a spark plug fouling index saved in a nonvolatile memory is updated. In an embodiment, the spark plug fouling index may be updated solely responsive to engine start. In another embodiment, the spark plug fouling index may be further updated based on engine operating parameters such as engine coolant temperature and engine run time. By saving the spark plug fouling index in the nonvolatile memory, the index may reflect spark plug fouling due to foreign substance accumulation during multiple engine run periods. The method may further include displaying a plug fouling indicator and flashing the indicator at a frequency based on the spark plug fouling index to show the severity of plug fouling. In response to spark plug fouling, an inspector may drive the vehicle along a planned route for a time period with both engine speed and engine load in a predetermined range to clean the spark plug. During the plug cleaning process, the spark plug fouling index and frequency of the plug fouling indicator may continue to be updated, so that the inspector may know the progress of the cleaning by checking the fouling indicator. The plug fouling indicator may be disabled upon finishing the plug cleaning process. In this way, status related to spark plug fouling may be indicated via a single indicator through the pre-delivery phase of the vehicle. By driving the vehicle along the planned route, fouled spark plug may be more effectively cleaned. After delivering the vehicle to the dealership, the vehicle may be set to a post-delivery mode, either manually or automatically. The spark plug fouling index may continue to be updated during the post-delivery phase and serve as a factor in determining ignition system health.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.